In recent years, cutting with high efficiency has been highly demanded. Accompanying with heightening of this demand, a cutting tool having a longer tool life than that of the conventional ones has been required. Thus, as characteristics required for the tool materials, it is important to improve characteristics relating to lifetime of a cutting tool. For example, it is more important to improve wear resistance and fracture resistance of the cutting tool. To improve these characteristics, a coated tool wherein alternately laminated films in which coating films are alternately laminated are formed on a substrate has been used.
To improve characteristics of such alternately laminated films, various techniques have been proposed. In Patent document 1, for example, a cutting tool in which a specific metal element or a compound thereof, and a specific alloy compound are laminated onto a surface of a base material with laminating cycles of 0.4 nm to 50 nm has been proposed. It has been disclosed that the cutting tool shows excellent wear resistance.
In Patent document 2, a cutting tool in which a first layer and a second layer are alternately laminated on a substrate so that these layers become 4 layers or more has been proposed. The first layer contains a complex nitride represented by the compositional formula of (Ti1-XAlX)N (X: 0.30 to 0.70 in an atomic ratio). The second layer contains an aluminum oxide phase and a titanium nitride phase. A ratio of the aluminum oxide phase in the second layer is 35 to 65% by mass based on the total of the aluminum oxide phase and the titanium nitride phase. Average thicknesses of the first layer and the second layer are each 0.2 to 1 μm. An average thickness of the first layer and the second layer in total is 2 to 10 μm. It has been disclosed that the cutting tool has excellent wear resistance.
In Patent document 3, a coated tool containing a first laminated structure and a second laminated structure has been proposed. The first laminated structure has a structure in which two or more layers having different compositions are periodically laminated. The average thickness of the respective layers contained in the first laminated structure is 60 nm or more and 500 nm or less. The second laminated structure has a structure in which two or more layers having different compositions are periodically laminated. The average thickness of the respective layers contained in the second laminated structure is 2 nm or more and less than 60 nm.